Bone and Soft Tissue Infections Flashcards
What are the types of osteomyelitis?
Acute, subacute or chronic
Specific or non-specific
In what people is acute osteomyelitis most common?
Mostly children, boys > girls
What is the acute osteomyelitis associated with?
History of minor trauma Diabetes Rheumatoid arthritis Immune compromise Long-term steroid treatment Sickle cell disease
What are the modes of spread of acute osteomyelitis?
Haematogenous spread in children and elderly
Local spread from contiguous site of infection e.g. trauma
Infants - infected umbilical cord
Children - boils, tonsillitis, skin abrasions
Adults - UTI, arterial line
What is the most common causative organism of acute osteomyelitis?
Infants < 1 - staph aureus, followed by group B strep, then E. coli
Older children - staph aureus, followed by streptococcus pyogenes then haemophilus influenzae
Adults - staph aureus, followed by coagulase negative staph, propionibacterium spp., strep pyogenes, mycobacterium tuberculosis etc.
What is commonly the causative organism of acute osteomyelitis in butchers?
Brucella
What is commonly the causative organism of acute osteomyelitis in fishermen and filleters?
Mycobacterium marium
In what patients is candida more commonly a causative organism of acute osteomyelitis?
Debilitating illness HIV/AIDS Long-term antibiotic treatment GI surgery Malignancy
What are the special cases of acute osteomyelitis where causative organisms would be different from the normal population?
Diabetic foot and pressure sores - mixed infection, including anaerobes
Vertebral osteomyelitis - staph aureus, TB
Sickle cell disease - salmonella species
STD - gonococcus
What is the pathology of acute osteomyelitis?
Starts at metaphysis
Vascular stasis
Acute inflammation causing increased pressure
Suppuration
Release of pressure (medulla, sub-periosteal, into the joint)
Necrosis of bone (sequestrum)
New bone formation (involucrum)
Resolution or no resolution and development into chronic osteomyelitis
Septic arthritis in the bone can also develop, most commonly in the hip and elbow
What is infected in acute osteomyelitis of long bones?
Metaphysis infected e.g. distal femur, proximal tibia, proximal humerus
What are the clinical features of acute osteomyelitis in infants?
Signs can range from minimal to severe illness Failure to thrive Drowsy or irritability Can be minimal signs or very systemically unwell Metaphyseal tenderness and swelling Reduced range of movement Positional change Commonest around the knee
What are the clinical features of acute osteomyelitis in children?
Severe pain Reluctant to move - not weight bearing May be tender, fever and tachycardia Malaise - fatigue, nausea and vomiting Toxaemia
What are the clinical features of acute osteomyelitis in adults?
Primary OM seen in thoracolumbar spine Backache History of UTI or urological procedure Elderly, diabetic or immunocompromised Unremitting pain - keeping patient awake at night
Secondary OM much more common
Often after open fracture or surgery
Mixture of causative organisms
Why do you need to be particularly aware of wounds that fail to heal and are likely to be infected that are close to the bone?
Because all of the necrotic tissue will need to be derided - both soft tissue and bone
What investigations should be done if suspecting acute osteomyelitis?
FBC and WBC - neutrophil leucocytosis
ESR
CRP
Blood cultures 3x at peak temperature, 60% positive
U&Es - ill, dehydrated
X-ray - not useful in acute presentation, can take 1-2 weeks to show, shows metaphyseal destruction at later dtage
US - more useful in hip if infection is in the joint
Aspiration
Isotope bone scan - non-specific
Labelled white cell scan - non-specific
MRI is the best investigation - accurate and good for determining the extent of infection
What are the differential diagnoses for acute osteomyelitis?
Acute septic arthritis
Trauma
Acute inflammatory arthritis
Transient synovitis
Rare - sickle cell disease, Gaucher’s disease, rheumatic fever, haemophilia
Soft tissue infection - cellulitis, erysipelas, necrotising fasciitis
What would be seen on the radiographs of a patient with acute osteomyelitis?
X-ray will be normal in first 10-14 days
Later will show increasing metaphyseal destruction
Early radiographs will show minimal changes
Early periosteal changes happen 10-20 days
Medullary changes occur in lytic areas
Late osteonecrosis - sequestrum
Late periosteal new bone - involucrum
What scans might be done for acute osteomyelitis?
Technetium-99m labelled bisphosphonate
Gallium 67 citrate delayed imaging
Indium-111 labelled WBC scan
MRI
What microbiology is done for acute osteomyelitis?
Blood cultures in haematogenous osteomyelitis and septic arthritis
Bone biopsy
Tissue or swabs from up to 5 sites around implant at debridement in prosthetic infections
Sinus tract and superficial swab results may be misleading due to skin contaminant
What is the treatment of acute osteomyelitis?
Supportive for pain and dehydration
Rest
Splintage
Antibiotics - IV/oral switch 7-10 days, 4-6 week duration oral antibiotics depending on response and ESR
Empirical antibiotics while waiting for cultures - flucloxacillin and benzylpenicillin
What does antibiotic choice depend on?
Spectrum of activity
Penetration to bone
Safety of long-term administration
Why might antibiotic failure occur?
Drug resistance e.g. beta-lactamases
Bacterial persistence e.g. dormant bacteria in dead bone
Poor host defences - diabetes, alcoholism
Poor drug absorption
Poor tissue perfusion
Drug inactivation by host flora
MRSA
What are the indications for surgery for acute osteomyelitis?
Aspiration of pus for diagnosis and culture
Abscess drainage - multiple drill holes, primary closure to avoid sinus
Debridement of dead/infected/contaminated tissue
Refractory to non-operative treatment > 24-48 hours - timing, drainage, lavage, infected joint replacements
What are the potential complications of acute osteomyelitis?
Septicaemia Death Metastatic infection Pathological fracture Septic arthritis Altered bone growth Chronic osteomyelitis
When does subacute osteomyelitis occur?
Increased host resistance
Lowered bacterial virulence
Antibiotic usage
What are the clinical features of subacute osteomyelitis?
Long history - weeks to months
Variable symptoms - pain, limp
Local swelling, occasionally warmth
Tenderness
What are the differential diagnoses for subacute osteomyelitis?
Tumour e.g. Ewing’s sarcoma, osteoid osteoma
TB
What are the features of Brodie’s abscess?
Subacute osteomyelitis
Older children
Painful limp, no systemic features
Radiographic lucency in long bone metaphysis
What are the differential diagnoses for Brodie’s abscess?
Ewing’s sarcoma
What are the investigations for subacute osteomyelitis?
X-ray
Bone scan
Biopsy - 50% positive
Grow organism
What is the treatment of subacute osteomyelitis?
Curettage
Prolonged antibiotics
When does chronic osteomyelitis occur?
May follow acute osteomyelitis
Much rarer in children
May start de-novo following an operation or open fracture, or in a patient with immunocompromise e.g. diabetes, elderly
What are the features of chronic osteomyelitis?
Repeated breakdown of healed wounds
Often mixed infection
Usually the same causative organism at each flare-up
Cavities, possible sinuses
Dead bone - retained sequestra
Involucrum
Histological picture of chronic inflammation
What are the most common causative organisms of chronic osteomyelitis?
Staph aureus still most common
E. coli
Strep pyogenes
Proteus
What is the treatment of chronic osteomyelitis?
Long-term antibiotics - local and/or systemic Eradicate bone infection surgically Treat soft tissue problems Deformity correction Massive reconstruction Amputation
What are the potential complications of chronic osteomyelitis?
Chronically discharging sinus and flare-ups
Ongoing infection - metastatic, abscesses
Pathological fracture
Growth disturbance and deformities
SCC in 0.07%
What is acute septic arthritis?
Infection in a joint
What are the modes of infection that cause acute septic arthritis?
Direct invasion from penetrating wound, intra-articular injury or arthroscopy
Eruption of bone abscess
Haematogenous spread
Metaphyseal septic focus - either septic arthritis or osteomyelitis
What are the most common causative organisms of acute septic arthritis?
Staphylococcus aureus most common
Strep pyogenes
Haemophilus influenzae
E. coli
What is the pathology of acute septic arthritis?
Acute synovitis with purulent joint effusion
Articular cartilage attacked by bacterial toxin and cellular enzyme
Complete destruction of the articular cartilage
What are the possible sequelae of acute septic arthritis?
Complete recovery
Partial loss of articular cartilage and subsequent OA
Fibrous or bony ankylosis
What are the features of acute septic arthritis in neonates?
Picture of septicaemia
Irritability
Resistant to movement - more painful than acute osteomyelitis due to build-up of pressure
Systemically unwell
What are the features of acute septic arthritis in children?
Acute pain in a single joint
Reluctant to move the joint in any way, consider bursitis where range of movement is normal
Increased temperature and pulse
Increased tenderness
What are the features of acute septic arthritis in adults?
Often involves a superficial joint
Rare in healthy adults
What are the investigations that should be done for acute septic arthritis?
FBC WBC ESR CRP Blood cultures X-ray US Aspiration
What is the most common cause of acute septic arthritis in adults?
Infected joint replacement
What are the complication of acute septic arthritis in adults?
Death
Amputation
Removal of arthroplasty
What is the most common causative organism of acute septic arthritis in adults?
Staph aureus
What are the differential diagnoses for acute septic arthritis?
Acute osteomyelitis Trauma Pseudogout Irritable joint Haemophilia Rheumatic fever Gout Gaucher's disease
What is the treatment of acute septic arthritis?
General supportive
Antibiotics 3-4 weeks
Surgical drainage and lavage - arthroscopic lavage or open operation in infected joint replacements, followed by antibiotics
What is tuberculosis of bones and joints due to?
Used to be due to TB, rickets and polio
Now due to trauma and degenerative joint disease
What is the typical presentation of tuberculosis of bones and joints?
Bent children - unable to stand straight
Thoracic kyphosis
Lower limb deformities
What are the classifications of tuberculosis of bones and joints?
Extra-articular - epiphyseal/bones with haemodynamic marrow
Intra-articular - large joints
Vertebral body - most common
Multiple lesions in 1/3rd
What are the clinical features of tuberculosis of bones and joints?
Insidious onset with general ill health Contact with TB Pain, especially at night Swelling Weight loss Low grade pyrexia Joint swelling Decreased range of movement (won't be seen in spine) Ankylosis Deformity
What is the pathology of tuberculosis of bones and joints?
Primary complex in lung or gut
Haematogenous secondary spread to bones
Tuberculous granuloma
Role of nutrition and influence of other diseases e.g. HIV, AIDS
What is the presentation of spinal tuberculosis?
Little pain
Abscess or kyphosis
How is TB of bones and joints diagnosed?
Long history Involvement of a single joint Marked thickening of the synovium Marked muscle wasting Periarticular osteoporosis
What investigations should be done for TB of bones and joints?
FBC ESR Mantoux tests Sputum/urine culture X-ray Joint aspiration and biopsy - AAFB identified in 10-20%, culture +ve in 50%
What are the features of the x-ray of a patient with TB of bones/joints?
Soft tissue swelling
Peri-articular osteopaenia
Articular space narrowing
What are the differential diagnoses for TB of bones and joints?
Transient synovitis
Monoarticular rheumatoid arthritis
Pyogenic arthritis
Haemorrhagic arthritis
What is the treatment of TB of bones and joints?
Chemotherapy
Rifampicin, isoniazid, ethambutol and pyrazinamide - 8 weeks, followed by rifampicin and isoniazid for 6-12 months
Rest and splintage
Operative drainage rarely necessary
